Research On Robust Disturbance Rejection Control Of Moving Mass Fixed-wing Unmanned Aerial Vehicle

Unmanned aerial vehicles(UAV)have made considerable progress in recent years due to their low production cost,simple design and manufacture,and ease of operation.Compared with the rotorcraft,the fixed-wing UAV has the advantages of long range,large load,and easy stealth.It has wider application prospects in the military and civilian fields.The moving mass control scheme generates the steering torque by changing the position of the mass slider inside the aircraft,and then completes controlling its states.Compared with traditional rudder surface control,moving mass scheme has certain advantages in maintaining aerodynamic efficiency,enhancing stealth capability and simplifying structure of wings.This paper takes a small moving mass fixed-wing UAV as the object,and considers its strong nonlinearity and coupling characteristics,and studies on its dynamics and robust anti-disturbance control problems.Firstly,the basic configuration of the single-slider moving mass UAV is designed,and then a complete motion function of the system is established based on Newton's law of motion and the momentum moment theorem,and the expressions of the forces and moments of the moving mass UAV are given.On this basis,the dynamic characteristics of the drone are analyzed through linearization,focusing on the impact of the initial installation position of the slider on the stability and maneuverability of the UAV.Then the ideal installation position of the slider is given,which providing a quantitative reference for the design of the slider mechanism.By further simulating and comparing the changing trend of the moving mass scheme and the traditional rudder scheme with the fight speed,it is pointed out that the moving mass scheme is more efficient for small UAVs with generally low speed.Subsequently,the model of the moving mass UAV control system in affine form is derived.In order to simplify the controller design problem,the coupling term is regarded as an unknown disturbance and superimposed on the system model.Based on this model,the active disturbance rejection controller(ADRC)of the moving mass UAV is designed,and the particle swarm optimization algorithm is introduced to optimize the parameters of the ADRC,so as to solve the problem of parameters setting.The simulation results indicate that the ADRC after optimization has significantly improved in reducing overshoot and increasing tracking speed.Considering the complexity of the parameters setting of the ADRC and its sensitivity to the relevant parameters,an adaptive sliding mode controller based on fuzzy system and neural networks is designed.For the unknown part of the UAV dynamic equations caused by parameter perturbation and external disturbances,RBF neural networks is used to accurately estimate it,and then completing the design of the sliding mode controller.For the chattering problem,the universal approximation feature of the fuzzy system is used to accurately approximate the switching items,thereby achieving smooth handling of chattering and improving the performance of the sliding mode controller.Finally,through the comparative simulation under various working conditions,it is verified that the control system designed for the moving mass UAV has strong robustness and anti-disturbance capability.It can effectively deal with various complex situations faced by the UAV during flight,and achieves the initial goal of controller design.